The present invention relates in general to liquid-crystal display devices, and, more particularly, to a method of aligning optical sheets in a thicknesswise direction of the liquid-crystal display device.
TFT-type liquid-crystal display modules, using thin film transistors (TFTs) as active elements, are broadly used as display devices, such as in personal computers, monitors and television receivers. These liquid-crystal display modules are each constituted by a liquid-crystal display panel arranged with a drive circuit in the periphery thereof and a backlight for illuminating the liquid-crystal display panel.
The backlights are roughly divided into two basic types, including the under-lighting type backlight, in which a that the cold-cathode fluorescent lamp is arranged underneath a light conductor, and the side-lighting type backlight, in which the cold-cathode fluorescent lamp is arranged at one side face of the light conductor. In both types of backlights, optical sheets (diffusion sheets, prism sheets) are arranged over the top surface (the liquid-crystal display panel side) of the light conductor.
Conventionally, for the purpose of fixing such optical sheets is positioned, a hole is formed in the optical sheets so that a projection formed in a sidewall of an optical-sheet accommodating mold can be inserted in the hole, followed by adhering a tape over the projection from above in order to fix the projection in the hole.
However, with this method, the adhesive tape is readily peeled off the projection because the area of the projection in contact with the tape is small in diameter. In the worst case, it is possible for the optical sheets to move in a thicknesswise direction of the liquid-crystal display device and fall out of the mold. Besides, there is the possibility of inferior production efficiency due to the need to paste an adhesive tape on the assembly.
In order to solve the foregoing problem, Document 1 (Japanese Patent Laid-Open Hei 11-337942) discloses a technique in which an engagement claw is formed at the head of an engagement piece so that the optical sheets can be prevented from falling out of the engagement piece due to the providing of the engagement claw.